This invention relates generally to the field of hard disc drive data storage devices, and more particularly, but not by way of limitation, to disc drive actuators.
Disc drives of the type known as xe2x80x9cWinchesterxe2x80x9d disc drives, or hard disc drives, are well known in the industry. Such disc drives magnetically record digital data on a plurality of circular, concentric data tracks on the surfaces of one or more rigid discs. The discs are typically mounted for rotation on the hub of a brushless DC spindle motor. In disc drives of the current generation, the spindle motor rotates the discs at speeds of up to 15,000 RPM.
Data are recorded to and retrieved from the discs by at least one read/write head assembly, also known as a head or slider, which are controllably moved from track to track by an actuator assembly. Where more than one head are used, an array of heads are typically vertically aligned. The read/write head assemblies typically comprise an electromagnetic transducer carried on an air bearing slider. This slider acts in a cooperative pneumatic relationship with a thin layer of air dragged along by the spinning discs to fly the head assembly in a closely spaced relationship to the disc surface. In order to maintain the proper flying relationship between the head assemblies and the discs, the head assemblies are attached to and supported by flexures attached to the actuator.
The actuator assembly used to move the heads from track to track has assumed many forms historically, with most disc drives of the current generation incorporating an actuator of the type referred to as a rotary voice coil actuator. A typical rotary voice coil actuator consists of a pivot shaft fixedly attached to the disc drive housing base member closely adjacent the outer diameter of the discs. The pivot shaft is mounted such that its central axis is normal to the plane of rotation of the discs. The actuator is mounted to the pivot shaft by a pivot assembly, which may take the form of precision ball bearing assemblies within a bearing housing. The actuator supports a flat coil which is suspended in the magnetic field of an array of permanent magnets, which are fixedly mounted to the disc drive housing base member.
On the side of the actuator bearing housing opposite to the coil, the actuator assembly typically includes one or more vertically aligned, radially extending actuator head mounting arms, to which the head suspensions mentioned above are mounted. These actuator arms extend between the discs, where they support the head assemblies at their desired positions adjacent the disc surfaces. When controlled DC current is applied to the coil, a magnetic field is formed surrounding the coil which interacts with the magnetic field of the permanent magnets to rotate the actuator bearing housing, with the attached head suspensions and head assemblies, in accordance with the well-known Lorentz relationship. As the actuator rotates, the heads are moved generally radially across the data tracks of the discs along an arcuate path.
As explained above, the actuator assembly typically includes an actuator body that pivots about a pivot mechanism disposed in a medial portion thereof. The function of the pivot mechanism is crucial in meeting performance requirements associated with the positioning of the actuator assembly. A typical pivot mechanism takes the form of a bearing cartridge having upper and lower bearings with a stationary shaft attached to an inner race and a sleeve attached to an outer race. The sleeve has typically been secured within a bore in the actuator body using a set screw, a C-clip, a tolerance ring or press-fitting, while the stationary shaft typically is attached to both the base deck and the top cover of the disc drive. It has also been contemplated that the bearing cartridge could itself be fixed to the base, while the actuator is attached to the pivot shaft which is free to rotate within the pivot cartridge housing, especially in the case of single stage actuators as will now be explained.
Recently, advances in storage technology have greatly increased the data storage capacity of magnetic storage discs. As a result, a single storage disc is now capable of storing large amounts of data which would have required a stack of several discs in the past. Some drive manufacturers have begun to produce disc drives having fewer discs, and even a single disc, as often a single disc may have storage capacity sufficient for a given application. In addition to the obvious cost advantages gained by using only one disc, one advantage to providing only one disc is that the actuator must carry only one or at most two heads. Such an actuator may have only one arm and therefore have a rotational inertia much smaller than that of conventional actuators with multiple arms. Moreover, an actuator with only one arm may be produced from a single planar sheet of material, supporting a coil at one end and a head suspension at another. This type of actuator may be more easily manufactured than conventional actuators, such as by stamping, and is further advantageous in that it has relatively low inertia, allowing faster seek acceleration and deceleration. On the other hand, a planar element is susceptible to vibration in the first bending mode, in which the member may bend in a direction perpendicular the plane in which it lies, giving it a relatively low resonant frequency, increasing read-write errors while decreasing drive reliability, often culminating in drive failure.
Drives having only one disc and one actuator arm also offer the opportunity to produce low-profile disc drives having a reduced height. In the past, disc drives were typically used for storage of data in personal computers and in storage arrays for storing huge amounts of data in enterprise applications. Presently, however, drives are being contemplated for use in a wide variety of consumer products, such as television set-top video recorders, video game consoles, and hand-held computers. These applications present a new set of challenges to the drive industry, requiring that drives be more quiet and smaller than ever before. In particular, there is a need to produce drives having a height which is decreased relative to that of conventional drives to enable use in hand-held and card-type applications.
As drive housings become smaller, however, space availability in the housing has decreased, especially in the vertical direction. Actuator pivot assemblies occupy vertical space, as do voice coil poles and magnets, and spindle motor and hub designs often limit the height at which a disc can be mounted. Often design requirements dictate the disc, magnets and actuator pivot be arranged such that a planar actuator is not capable of being properly aligned with both the disc and VCM.
What the prior art has been lacking is a planar actuator with increased bandwidth and the ability to fit into increasingly low-profile disc drives.
The present invention is directed to a dual plane single-stage actuator. The actuator includes a step portion between the coil and head support portions, which increases its stiffness while permitting the coil support portion and head support portion of the actuator to lie in different planes. This allows the actuator to be installed in low-profile drives.
These and other features and benefits will become apparent upon review of the following figures and the accompanying detailed description.